Field of the Disclosure
Embodiments disclosed herein relate generally to centrifuges manufactured using composite materials. More specifically, embodiments disclosed herein relate to centrifuges manufactured using high strength composite materials.
Background
Solid bowl decanting centrifuges are often used to separate liquid-solid mixtures. For example, well drill cuttings, drilling mud, slop oil, and other waste generated during drilling of wells and general chemical processing may be separated using a centrifuge. Such mixtures may include solids and one or more of oleaginous fluids and aqueous fluids.
The principle of centrifuge operation relies on the density difference between the solids and the liquids within a drilling fluid. As a rotational torque is applied to a centrifuge generating a centrifugal force (hereinafter, “G force”), the higher-density solids preferentially accumulate on the outer periphery inside the centrifuge, whereas the lower-density liquids preferentially accumulate closer to the axis of the centrifuge rotation. On the initial separation by the G force, the solids and the liquids can be removed from opposite sides of the centrifuge using a ribbon-type screw conveyor, sometimes referred to as a scroll.
Some challenges facing the operation of a centrifuge include high feed rates and varying solids content in the feed. As the feed rates increase, high speed and torque is typically required to accomplish the solids separation, thus resulting in increased footprint due to equipment size, and increased energy and operational costs. Wear and tear is also a concern due to effects of abrasive and corrosive materials in the feed, particularly where fluids and solids scrape against centrifuge components during operation.
In addition, centrifuge components must be able to maintain strength and rigidity during high speed operation in order to reduce deformation of the components, which eventually causes system vibrations and component breakdowns. Thus, conventional centrifuge components are typically made from stainless steel or carbon steel alloy components. Bowls, for example, are conventionally made from stainless steel and may weigh in excess of 300 lbs. However, the size and weight of stainless steel centrifuge components are problematic. At the high rotational speeds required for high separation efficiency, most of the bending stress on the bowl derives from the “G” force acting on the weight of the steel bowl wall itself. Making the bowl thicker just increases this stress. Secondly, due to their size and weight, centrifuge components are expensive to manufacture and ship, as well as cause safety concerns due to the high rotational speed of the components. Thirdly, due to the size and weight of centrifuge components, additional costs are incurred for oversized drive and related support components that are sufficient to maintain the structural integrity of the centrifuge during operation.
Another concern with conventional centrifuges is the expense of the components. As discussed, the components are typically made from stainless steel and other costly alloys, which are expensive to manufacture and maintain. In addition, the components must be manufactured with high precision because of the high G forces occurring during operation, which further increases the cost of conventional centrifuge components.
The expense of conventional centrifuge components is compounded by the fact that centrifuge components are expensive to maintain and repair. As discussed previously, components are subject to wear due to corrosion and mechanical abrasion, among other factors. For example, the repetitive high G forces during operation may cause components to warp or distort over time. This wear negatively affects the precision of the components, thereby requiring maintenance or replacement to keep the centrifuge in operational condition. However, it is often difficult and time consuming to remove and/or replace centrifuge components. This often leads to re-welding and re-machining of parts at the jobsite, which can result in increased machine vibrations and significant centrifuge downtime.
Accordingly, there exists a need for improved centrifuges and improved methods for separating oilfield solids and liquids.